1. Field of the Invention
This invention relates to a fuel pump for a high-pressure fuel injection system, more particularly to a fuel pump for a high-pressure fuel injection system with an improved relief valve function.
1. Prior Art
A conventional direct gasoline injection system or other such high-pressure fuel injection system has a high-pressure fuel pump and a pressure control valve (solenoid valve unit) for controlling the fuel pressure, and is further equipped with a relief valve for preventing abnormal pressure rise in the high-pressure fuel pump should the fuel passage be blocked for some reason at or downstream of the discharge port.
Since the relief valve is set to a pressure that is at least 10% higher than normal operating pressure, however, the pump components are subjected to a corresponding overload.
In addition, provision of the relief valve as an add-on component increases costs and also involves the risk that leakage from the relief valve may lower system performance.
This invention was accomplished in light of the foregoing problems of the prior art and has as one of its objects to provide a fuel pump for a high-pressure fuel injection system whose high-pressure fuel pump can secure a relief function without separate installation of a relief valve.
Another object of the invention is to provide a fuel pump for a high-pressure fuel injection system whose pressure control valve for controlling the fuel pressure of the high-pressure fuel pump is provided with a pressure relief function.
Another object of the invention is to provide a fuel pump for a high-pressure fuel injection system whose structure is optimal for providing the pressure control valve with a pressure relief function.